Tuesday, 6 November 2018

What Does it Take to Be a Brain Disorder?

In this post, Anneli Jefferson, Leverhulme Early Career Fellow at the University of Birmingham summarizes her paper on the nature of brain disorder, recently published in Synthese.

A long-standing project pursued by some psychiatrists is to show
that mental disorders are brain disorders and that mental dysfunction can best
be explained as brain dysfunction. But what exactly is the relationship between
mental disorders and brain disorders and when is a mental disorder a brain disorder? This is the question I address in my paper. Some psychiatrists believe that it follows from the acceptance of physicalism
that all mental disorders are brain disorders. If all mental states are brain
states, shouldn’t all disordered mental states be disordered brain states?

Many philosophers have resisted this conclusion, appealing
to the hardware/software distinction to argue that even if dysfunctional mental
processes are realised in the brain, this does not mean that the underlying
brain processes are also disordered. Just as there can be a software problem
without there being anything wrong with the hardware, there can in principle be
a mental problem without any systematic problem in brain function.

This argument is often supported by appeal to multiple realizability: one mental
dysfunction can be realised by many different brain processes in different
individuals or in one individual over time. There may not be a stable underlying
brain pattern that realises a specific psychological dysfunction.

In the paper, I suggest that when we do find an underlying
brain difference that realises psychological dysfunction, we should
characterize this as a brain dysfunction because it realises mental
dysfunction. This means that in some cases (for example, amygdala hypofunction)
the characterisation of brain difference as dysfunctional is derivative of the
psychological level, because the reason the brain anomaly is characterized as
dysfunctional is purely that it realises psychological dysfunction.

There is no
independent, brain-internal criterion that characterizes these differences as
dysfunctional, instead the characterization of brain dysfunction depends on the
psychological level. This should not worry us, I argue, because the brain is
the organ of thought, so it stands to reason that we look at the interaction
between disordered processes of thought and feeling and brain anomaly when
figuring out which brain differences constitute brain dysfunctions.

While my account provides us with a principled way of saying
that there is something wrong with the brain, it does not do a lot of things
many people think an account of brain disorder and dysfunction should do. Most importantly, it does not give us a purely
physiological notion of brain dysfunction which does not rely on the
psychological level for ascriptions of dysfunction.

As authors like George
Graham (2013) have pointed out, the notion of brain
disorder and dysfunction that derives from that of mental dysfunction and disorder is not well-suited for explaining mental dysfunction
as resulting from some temporally and logically prior mechanical brain defect.

The
paradigmatic model of brain disorders is that of neurodegenerative conditions
or brain tumours, where there is a clearly identifiable physiological problem
which also causes psychological dysfunction and which is cured by physiological
means. Some philosophers believe that brain disorders are only those conditions where we can provide purely physiological causes for the onset
of a mental health condition or a cure through medication or other kinds of
physical intervention.

My account encompasses paradigmatic brain disorders, but
is more permissive. Anyone who wants their account of brain disorders to include
all, and only, conditions where we can give account of brain dysfunction independently
of psychological criteria, will not be satisfied with my account.

However, as I
explain in the paper, I take this goal to be mistaken, as even standard
accounts of physiological dysfunction often rely on more large scale problems
that a physiological anomaly causes for the person. We should therefore adopt
an account which aims to classify those conditions as brain disorders for which we
can justifiedly say that there is something wrong with the brain.